3Com Switch 8800 Configuration Guide Chapter 38 MSTP Region-configuration38-1Chapter 38 MSTP Region-configuration38.1 Introduction to MSTPMSTP stands for Multiple Spanning Tree Protocol, which is compatible with SpanningTree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP).STP is not fast in state transition. Even on a point-to-point link or a edge port, it has totake an interval twice as long as forward delay before the port transits to the forwardingstate.RSTP converges fast, but has the following drawback like STP: all the network bridgesin a LAN share one spanning tree and the redundant links cannot be blocked based onVLANs. Packets of all VLANs are forwarded along one spanning tree.MSTP makes up for the drawback of STP and RSTP. It not only converges fast, but alsoallows the traffic of different VLANs to be distributed along their respective paths, whichprovides a better load-balance mechanism for the redundant links.MSTP keeps a VLAN mapping table to associate VLANs with their spanning trees.Using MSTP, you can divide one switching network into multiple regions, each of whichcan have multiple spanning trees with each one independent of others. MSTP prunesthe ring network into a loopfree tree to avoid the generation of loops and infinitecirculations. It also provides multiple redundant paths for data forwarding to implementthe load-balance mechanism of the VLAN data.38.1.1 MSTP ConceptsThere are 4 MST regions in Figure 38-1. Each region consists of four switches, all ofwhich run MSTP. The following introduces the concept of MSTP with the help of thisfigure.
